Underdrive Pulleys?

ThoR_ · 01-10-2007, 09:22 PM

Hey guys i have a AU XR8 200kw series 2. Im just wondering if anyone would have any idea how much more HP an under drive pulley would give me, has anyone done it?

Cheers

fairBA · 01-10-2007, 09:40 PM

20% hp I think from reading other peoples post -check the B series section, quit popular there
happy to be corrected though

philstoj · 01-10-2007, 10:38 PM

None available for the Explorer/AU V8 engines, they have a factory underdrive set already.

ThoR_ · 01-10-2007, 11:09 PM

hmmm ok ill check it out.

philstoj · 01-10-2007, 11:55 PM

Checkout what? As i said, they already have underdrive pulleys from the factory, stock, so look else where for gains, like 1.72 roller rockers, extractors and exhaust, edit...

schnoods · 02-10-2007, 12:57 AM

Quote:

Originally Posted by fairBA

20% hp I think from reading other peoples post -check the B series section, quit popular there
happy to be corrected though

I wish my underdrives gained that much!

I have em on an EF 5.0L and gained about 20 rwkw with an exhaust and headers. I reckon the exhaust and headers were good for 15, but you do notice the quicker pick up with the underdrives.

ThoR_ · 02-10-2007, 01:14 AM

bugga....thats that mod gone.

FTe_XR8 · 02-10-2007, 03:20 AM

Quote:

Originally Posted by philstoj

None available for the Explorer/AU V8 engines, they have a factory underdrive set already.

im prob wrong here but i know u can buy underdrive pulleys for AU's or are they the same size just machined to look nicer?

ClassicAU · 02-10-2007, 08:53 AM

Would these make any difference on an I6 at all? I know the BA crew have been all over them for a while. I have always wondered if it is worthwhile on the trust SOHC at all?

Evan

Casper · 02-10-2007, 09:29 AM

AU I6 is under driven from the factory as well.

ClassicAU · 02-10-2007, 12:35 PM

Fair enough, thanks Casper. To be honest, I have no idea what it even is! I have just heard it around the place and it sounds cool!

:

Evan

Casper · 02-10-2007, 12:41 PM

Well, technically its impossible to be "underdriven" from the factory.. as that is the stock pulleys. What I should say is that the pulleys on the AU I6 are already running as slow as you want them to go. If you "underdrive" them anymore you will find you get issues.

For the record it simply means to change the crank pulley (and accessory pulleys in some cases) to make things like your Powersteering, AC and water pump run slower than it did stock when the engine is going. This means it drains less power from the engine and can spin up through the rpm's quicker. Of course everything has a price and, if run too slow, you can find you have issues with Power steering and overheating. Its a fine line.

ThoR_ · 02-10-2007, 05:18 PM

Casper....dont you want a smaller whell though to run everything faster? to free up more hp? Sorta dun make sense but thats what i was told :S

JC · 02-10-2007, 05:43 PM

Quote:

Originally Posted by ThoR_

Casper....dont you want a smaller whell though to run everything faster? to free up more hp? .....but thats what i was told :S

Which wheel? Who told you? You seem to come across alot of dodgy information and present it as "that's what I was told". At some stage you (or at least a reasonable person) would have to think that if it's the same person telling you stuff, and they keep turning out to be wrong, then maybe one day you will stop listening to them and stop quoting them: "that's what I was told".

Technically the advice you have been given is in fact correct, but what people are saying to you here is that while underdrive pulleys are generally smaller than the factory spec ones, the reason they work on e-series (v8s) etc is because they came with rather large pulleys standard, and the underdrive pulleys they end up with are roughly the same size as the AU pulleys. So, if you fitted the underdrive pulleys suited to e series cars to an AU, you would not find any difference as they are close enough to the same size as AU pulleys anyway. OK, you may gain 1 kw or so, but at what $$$$ cost - I suppose then at least you can say you have aftermarket underdrives on "just like the B series boys". And you could surely source a set significantly smaller than the AU pulleys, and get some more power savings, but then you will hit the issues outlined above (heating issues, power steering issues etc).

xr8ute · 03-10-2007, 12:26 AM

Speaking of dodgy information.....anyone actually measured the ratio of the AU V8 pulleys and the E-Series V8 pulleys(crank to alt, and crank to ps)??

I have.

The AU power steering pump turns at a ratio of 1.16:1 (to the crank), and the EB at a ratio of 1.09:1.

The AU alternator turns at a ratio of 2.68:1, and the EB at a ratio of 2.7:1.

In fact, only the alternator is driven less, and that is by less than 1% compared to the EB!! Hmm.....hardly "underdriven".

Got to love a good internet myth :P

schnoods · 03-10-2007, 12:41 AM

Most of the parasitic power loss is from the waterpump.

xr8ute · 03-10-2007, 12:48 AM

Quote:

Originally Posted by schnoods

Most of the parasitic power loss is from the waterpump.

Hmm....forgot to measure the water pump pulleys. Will check them tomorrow.

philstoj · 03-10-2007, 01:11 AM

Quote:

Originally Posted by xr8ute

Speaking of dodgy information.....anyone actually measured the ratio of the AU V8 pulleys and the E-Series V8 pulleys(crank to alt, and crank to ps)??

I have.

The AU power steering pump turns at a ratio of 1.16:1 (to the crank), and the EB at a ratio of 1.09:1.

The AU alternator turns at a ratio of 2.68:1, and the EB at a ratio of 2.7:1.

In fact, only the alternator is driven less, and that is by less than 1% compared to the EB!! Hmm.....hardly "underdriven".

Got to love a good internet myth :P

Ive actually compared the pullies on my ute with a set of march underdrive pullies years ago, contemplating fitting on mine, but found that the AU ones were actually smaller, so instead, my mate fitted them to his ED XR8 Sprint...

I have looked before for a set to suit Explorer/AU engines and havent come across any, and then all the info on them over the years, they are underdriven enough and there is no need to underdrive them anymore...

Plenty of other areas to look for performance on these buggers.

ThoR_ · 03-10-2007, 01:15 AM

Quote:

Originally Posted by JC

Which wheel? Who told you? You seem to come across alot of dodgy information and present it as "that's what I was told". At some stage you (or at least a reasonable person) would have to think that if it's the same person telling you stuff, and they keep turning out to be wrong, then maybe one day you will stop listening to them and stop quoting them: "that's what I was told".

Technically the advice you have been given is in fact correct, but what people are saying to you here is that while underdrive pulleys are generally smaller than the factory spec ones, the reason they work on e-series (v8s) etc is because they came with rather large pulleys standard, and the underdrive pulleys they end up with are roughly the same size as the AU pulleys. So, if you fitted the underdrive pulleys suited to e series cars to an AU, you would not find any difference as they are close enough to the same size as AU pulleys anyway. OK, you may gain 1 kw or so, but at what $$$$ cost - I suppose then at least you can say you have aftermarket underdrives on "just like the B series boys". And you could surely source a set significantly smaller than the AU pulleys, and get some more power savings, but then you will hit the issues outlined above (heating issues, power steering issues etc).

you never have anything nice to say so if you dont...shut ya hole.....and dont post in my threads.

:

JC · 03-10-2007, 12:22 PM

Quote:

Originally Posted by ThoR_

you never have anything nice to say so if you dont...shut ya hole.....and dont post in my threads.

:

Are you serious? I'll bet I can find lots of members who disagree with your statement, and would challenge the quality of 99% of posts and threads that you have "contributed" to. And BTW, a thread started by you is not yours, so anyone who wants to can post in it.

You should try reading AND understanding the answers you have been given and instead of questioning the good advice you get on here, start questioning the poor advice you are getting elsewhere, starting with the mirror.

Casper · 03-10-2007, 02:50 PM